Need help replicating this XO in VituixCad

[bunkbail]

I'm getting confused as to where the ground is. Is it the middle line? And it seems like this XO is using a transformer (coupled iron core inductors) in the woofer circuit and it is not a thing in VituixCad?

PS: The crossover was taken from the article on the Solstice MLTL "improved" crossover by Rich Modafferi in audioXpress Dec 21 issue.

 

[Rick Sykora]

I'm getting confused as to where the ground is. Is it the middle line? And it seems like this XO is using a transformer (coupled iron core inductors) in the woofer circuit and it is not a thing in VituixCad?

PS: The crossover was taken from the article on the Solstice MLTL "improved" crossover by Rich Modafferi in audioXpress Dec 21 issue.


View attachment 335828

This is a series crossover and the "ground" is the lower left input. Agree there does not appear to be a way to add that transformer in VCAD (except as individual inductors). Does the article not detail why that transformer was used? Do not have access to the article.

 

[bunkbail]

This is a series crossover and the "ground" is the lower left input. Agree there does not appear to be a way to add that transformer in VCAD (except as individual inductors). Does the article not detail why that transformer was used? Do not have access to the article.

It did. It refers to this patent where Modafferi implements an infinite-order band(?) pass filter using the transformer but the details are a bit over my head. The patent explains what the new suggested crossover does to the Solstice MLTL in detail.

 

[Rick Sykora]

It did. It refers to this patent where Modafferi implements an infinite-order band(?) pass filter using the transformer but the details are a bit over my head.

Thanks, looks as though you need someone with more background than I on this one! Even then, not sure can be represented in VCAD.

Will copy @kimmosto as he would be the ideal reference.

 

[Rick Sykora]

Thanks, looks as though you need someone with more background than I on this one! Even then, not sure can be represented in VCAD.

Will copy @kimmosto as he would be the ideal reference.

Looking at it more closely, am mistaken on the topology as the schematic layout is unusual. Still do not know what to do with that transformer!

The 17 mH inductor is going to be heavy in any case. Do you have the Solstice or just contemplating?

 

[bunkbail]

Just contemplating but heavily considering the prospect. Here's the pic of the new crossover assembled (taken from the article).

 

[Rick Sykora]

Just contemplating but heavily considering the prospect. Here's the pic of the new crossover assembled (taken from the article).
View attachment 335845

No traditional transformer in this pic, it appears to have been implemented as individual inductors. In this case, the 2 solid core ones in the middle of this pic. Could try that approach in VCAD, but unless you have driver measurements as they are mounted on the baffle, is not going to be very accurate.

 

[bunkbail]

No traditional transformer in this pic, it appears to have been implemented as individual inductors.

Yeah I did mention that in the OP. But the close arrangement of the inductors means it is now a transformer and no such arrangements can be done in VituixCad, am I right? So the supposedly infinite-slope filter can't be simulated through the software...

 

[Rick Sykora]

This cross coupling aspect intrigues me. Would interesting to take that portion of the circuit and measure it. Earliest I could get to it is next week and will have to see if I have a couple of matching inductors. If not, sure I know someone who does.

Bagby’s crossover is a simple traditional one. Have you tried it in VCAD? Jeff had a reputation for simple, well designed crossovers. Before I bought my CBTs, the Solstice was one my short list to build. I would have used an active crossover though. Did you ask around the PE forum and see if anyone has measured the drivers?

 

[kimmosto]

Not sure about K=0.15 but otherwise this could replicate most of the original features.

Creates this kind of TFs with constant flat ZMA of 8 Ohms. Reality is a bit different of course due to complex curvy impedances.

 

[Rick Sykora]

Not sure about K=0.15 but otherwise this could replicate most of the original features.
View attachment 335999

Creates this kind of TFs with constant flat ZMA of 8 Ohms. Reality is a bit different of course due to complex curvy impedances.
View attachment 336000

Thanks Kimmo!

 

[kimmosto]

P.S. I would not use that topology for new design or redesign. Simple traditional parallel ladder is much easier to control. Series XO could drive designer grazy.

 

[kimmosto]

Probably quite close to the same slopes with parallel ladder XO. Final design and component values requires full measurements of actual system and some data processing.

 

[Rick Sykora]

Probably quite close the same slopes with parallel ladder XO. Final design and component values requires full measurements of actual system and some data processing.
View attachment 336029

Thanks again for sharing your time and expertise.

Happy Holidays!

 

[bunkbail]

Just seen the conversation. Thank you so much for chiming in and for the expertise @kimmosto and for your contribution as well @Rick Sykora

 

[Rick Sykora]

Just contemplating but heavily considering the prospect. Here's the pic of the new crossover assembled (taken from the article).
View attachment 335845

The large inductor on the left is about $30 each and weighs 2 lbs btw.

 

[killa25]

Just contemplating but heavily considering the prospect. Here's the pic of the new crossover assembled (taken from the article).

I have a pair of solstice in front of me as we speak! What I don't get about this article and "improved crossover" is that it claims to correct the phase at the crossover. As far as I know the phase is a function of the speakers response not the crossover. Using the crossover to change the response does change the phase but that is just because the response was changed. Two different types of crossovers that achieve the same response will have the same phase.
Also any competent modern designed crossover takes the phase at the crossover into account and phase should be aligned through the crossover. The easy way to correct phase is to go active

The designer of the solstice (Jeff Bagby RIP) was great crossover designer and I assure you that the phase was taken care of properly.

These are really revealing speakers. Well worth the price.

 

[killa25]

I'm getting confused as to where the ground is. Is it the middle line? And it seems like this XO is using a transformer (coupled iron core inductors) in the woofer circuit and it is not a thing in VituixCad?

PS: The crossover was taken from the article on the Solstice MLTL "improved" crossover by Rich Modafferi in audioXpress Dec 21 issue.


View attachment 335828

The ground is the bottom left circle point the input arrow is pointing to. The positive would be the top left circle that the input is pointing to. This is a series circuit rather than the typical parallel circuit found in the majority of crossovers including the Solstice. What I don't understand is the "transformer" looking part?

 

[bunkbail]

it claims to correct the phase at the crossover

The author made a few claims without much concrete evidence. The only reason I was intrigued by the speakers is that the author was the chief engineer of Joseph Audio and the engineer behind the infinite slope topology implemented in Joseph Audio speakers. He also claimed that his modified Solstice sonically rivals his set of the top-of-the-line Joseph Audio Pearls. I've not heard the Pearls, but the cheaper Joseph Audio Perspectives were one of the most beautifully sounding speakers I've ever heard.

Not sure about K=0.15 but otherwise this could replicate most of the original features.

So I've looked into this a bit and apparently K means coupling factor of the inductors and K value of 1 means perfect coupling between the inductors. Transformers specifically made for audio use typically has very high K value but this is not desirable in this topology since lower K value resulted from using 2 identical inductors can achieve steeper filtering slope and help mitigate distortion induced by the use of iron core inductors. The calculation of K value is over my head however. Fortunately in the article the author shared on how to mount the inductors (ERSE 18 AWG) with the exact spacing and orientations in order to get the desired K value.

 

[Rick Sykora]

The AE author likely had some stock of Erse inductors. The company owner passed and the Erse brand was hijacked by a chinese supplier. If you end up wanting to try, can help but will have to use US Coil equiv. As Kimmo mentioned, the DIY transformer seems like more hassle. Am not a huge fan of 2.5 crossovers but just may be the older BG speaker I bought (currently redesigning). If I recall correctly, Babgy considered a 2.5 way crossover for the Solstice and abandoned it.

Am guessing the Joseph Audio stuff is a bit beyond your price point?